Advances in Titanium Technology: Invited Presentations
Sponsored by: TMS Structural Materials Division, TMS: Titanium Committee
Program Organizers: Don Li, Howmet Engineered Products; Yufeng Zheng, University of North Texas; Peeyush Nandwana, Oak Ridge National Laboratory; Matthew Dunstan, US Army Research Laboratory
Wednesday 8:30 AM
March 17, 2021
Room: RM 30
Location: TMS2021 Virtual
Session Chair: Don Li, Howmet Engineered Products
8:30 AM Invited
Titanium Mill Product Yield Enhancement via Electrochemical Conditioning: Kurt Faller1; 1MetCon
A new mill product conditioning process has been developed and patented by MetCon; arguably the most dramatic cost reduction for production of metallic titanium in 30 years. The novel electrochemical process has been industrially commercialized for titanium mill products as an alternative to midwest grinding or machining techniques. The “MetCon Process” involves submerging the metal workpiece in an aqueous electrolyte of carboxylic acid + a fluoride salt while connected to a DC power supply, immersing the opposing electrode of the power supply in the bath, and applying current across the bath. 10% to greater than 15% more finished mill product from starting ingot is generated due to yield improvements compared to traditional conditioning. With minor changes, the technology can additionally be used as a green alternative to traditional hydrofluoric plus nitric acid pickling, addressing environmental and occupational hazards.
8:50 AM Invited
Optimizing Microstructure and Properties of Additively Manufactured Titanium Alloys Using Alloying and Post-AM Heat-treatment: Brian Welk1; Nevin Taylor1; Gopal Viswanathan1; Hamish Fraser1; 1Ohio State University
It has been recognized that additively manufactured Ti alloys are most usually characterized by the presence of very coarse columnar grains, oriented in the build direction. The solution that has been developed in our current research involves the application of computational thermodynamics to identify which alloying additions to titanium alloys result in an increase in the freezing range of the given alloy base, such that a columnar to equiaxed transition (CET) may be effected. These alloying additions, which are mainly beta eutectoid formers, when added in critical concentrations cause a CET to occur, resulting in a relatively fine equiaxed microstructure. The amounts of required solute additions usually exceeds their solubility limits, and, so, heat-treatments are required subsequent to the additive manufacturing process. Two types of alloys are being developed, the first with essentially identical properties as the (given) base alloy, and the second, alloys with enhanced mechanical properties.
9:10 AM Invited
Multiscale Characterization of Titanium Alloy Microstructures and Links to Processing and Properties: Amy Clarke1; Benjamin Ellyson1; Alec Saville1; Jonah Klemm-Toole1; Behnam Aminahmadi1; Jake Benzing2; Adam Creuziger2; Sven Vogel3; Kamel Fezzaa4; Wayne Chen5; Adam Pilchak6; 1Colorado School of Mines; 2National Institute of Standards and Technology; 3Los Alamos National Laboratory; 4Advanced Photon Source, Argonne National Laboratory; 5Purdue University; 6Air Force Research Laboratory
Titanium (Ti) alloys are ubiquitous in the aerospace, defense, and biomedical industries. Today, state-of-the-art characterization techniques available in the laboratory and at national user facilities are enabling unprecedented, multiscale in-situ/ex-situ studies of Ti alloys and new insights into processing-microstructure-property-performance relationships. Multiscale characterization of Ti-6Al-4V built by additive manufacturing (AM) reveals alpha-phase texture changes with scan strategy, typical {001} solidification texture revealed by beta-phase reconstruction, and varying (cube and fiber) beta-phase textures and grain morphologies produced by raster (large columnar grains) and spot (finer columnar and globular grains) melt strategies, linking processing to microstructure evolution and revealing possible strategies for microstructure and property control during AM. We also explore the role of omega-phase and transformation- and twinning-induced plasticity, or TRIP/TWIP, on the mechanical response of metastable Ti alloys after/during quasi-static or dynamic testing. These deformation mechanisms can be tailored to design properties and performance of Ti alloys for engineering applications.
9:30 AM
Atom Probe Tomographic Study of Precursor Metastable Phases and Their Influence on α Precipitation in the Metastable β-titanium Alloy, Ti-5Al-5Mo-5V-3Cr: Stoichko Antonov1; Yufeng Zheng2; Hamish Fraser3; Baptiste Gault1; 1Max Planck Insitut fur Eisenforschung GmbH; 2University of Nevada, Reno; 3The Ohio State University
The microstructural evolution and mechanical performance of metastable β-titanium alloys can be significantly influenced the thermo-mechanical treatment, causing formation of various nano-scaled phases. The exploration of these phases in β-Ti alloys, and their interplay with the ⍺ phase, is tremendously important as a lever to tailor the microstructure, and consequently the mechanical properties. In this study, we used in-situ and ex-situ conventional and aberration-corrected scanning/transmission electron microscopy and atom probe tomography to characterize the cascade of metastable phases forming in Ti-5Al-5Mo-5V-3Cr during heating to aging temperature, as well as their influence on the ⍺ distribution. The results show that the nucleation of ⍺ is strongly influenced by phases formed by diffusional-displacive transformations and are rich in Ti - ⍵, ⍺ʺ, and Oʺ - that serve as intragranular nucleation sites for ⍺. This work paves the way for exploiting this cascade of metastable phases for further microstructural engineering of Ti-alloys.
9:50 AM
An In-situ Deformation Micro-mechanisms Study of a Ti-Al-V-Fe (α+β) Alloy: Shaolou Wei1; Gaoming Zhu1; Cem Tasan1; 1Massachusetts Institute of Technology
Two-phase titanium alloys witness a wide range of engineering applications, due to the broad spectrum of microstructures and mechanical properties that they can exhibit. Their underlying deformation micro-mechanisms still stimulate profuse scientific interest because: (1) the pronounced plastic anisotropy of the α phase; and (2) the morphology and distribution of the β-phase. In this presentation, we aim to clarify the deformation micro-mechanisms of a Ti-Al-V-Fe (α+β) alloy with strongly textured α-phase and granular-shaped β-phase. Through integrated in-situ microstructure-based strain mapping technique, crystallographic calculation, and elasto-visco-plastic self-consistent simulation, we aim to address the following three topics: (1) what is the predominant deformation module and how its activation and transfer lead to strain heterogeneity? (2) what role do α and β phases play in plastic strain accommodation and partitioning? (3) what is the micro-mechanical origin for damage nucleation? In addition, further inspirations for mechanically-driven microstructural design strategy will also be covered.
10:10 AM
Enhanced Work-hardening from Oxygen-stabilized Omega Precipitation in Aged Metastable Beta Ti Alloys: Kathleen Chou1; Emmanuelle Marquis1; 1University of Michigan
Omega phase formation in metastable beta titanium alloys is known to cause significant ductility loss and embrittlement. Omega precipitates, which form rapidly during quenching and low temperature ageing, are therefore typically avoided in final microstructures after heat treatment. However, our recent work has shown that elevated levels of interstitial oxygen in Ti-Nb based alloys increases the work hardening capability during compression of these alloys with isothermal omega phase formation. In this work, commercial alloys Ti-15Mo and Ti-15-3-3-3 were investigated to understand omega formation with interstitial oxygen obtained through an oxidation exposure prior to ageing. The subsequent effect of omega precipitates with oxygen on mechanical properties was assessed using micropillar compression testing. Ageing treatments were selected to promote rapid isothermal omega precipitation and fast elemental partitioning. The results from this work may mitigate omega’s known detrimental effects on mechanical properties and enable new heat treatment design strategies for beta titanium alloys.